Notes Payable and Other Borrowings - Narrative (Detail) R$ in Millions										3 Months Ended		6 Months Ended
	Apr. 02, 2025 USD ($)	Jun. 10, 2024 USD ($)	Apr. 01, 2024 USD ($)	Mar. 12, 2024 USD ($)	Mar. 08, 2024 USD ($)	Oct. 06, 2023 USD ($)	May 22, 2023 USD ($)	Sep. 27, 2019 USD ($)	Aug. 23, 2017 USD ($)	Jun. 30, 2025 USD ($)	Jun. 30, 2024 USD ($)	Jun. 30, 2025 USD ($)	Jun. 30, 2024 USD ($)	Dec. 31, 2024 USD ($)	Dec. 06, 2024 USD ($)	Aug. 21, 2024 USD ($)	Jun. 07, 2024 USD ($)	Apr. 26, 2024 USD ($)	Oct. 19, 2023	Oct. 07, 2023 USD ($)	May 25, 2023 USD ($)	May 22, 2023 BRL (R$)	Mar. 10, 2022 USD ($)	Aug. 20, 2021 USD ($)	Aug. 20, 2021 BRL (R$)	Jul. 10, 2020 USD ($)	Feb. 26, 2020	Nov. 28, 2018 USD ($)	Aug. 06, 2018 USD ($)	Mar. 19, 2018 USD ($)	Aug. 23, 2017 BRL (R$)
Debt Instrument [Line Items]
Long-term debt										$ 1,836,090,000		$ 1,836,090,000		$ 1,141,709,000
Line of credit, maturity date extension (in years)																											2 years
Deferred financing cost										16,700,000		16,700,000		12,000,000.0
Carrying amount of debt component										1,917,835,000		1,917,835,000		1,337,540,000
Redemption price as percentage of principal amount (as a percent)								101.00%
Revolving credit facility | BGC Credit Agreement | Related Party
Debt Instrument [Line Items]
Line of credit facility, outstanding amount										0		0		0
Average interest rate (as a percent)				6.92%	1.00%
Interest expense recorded										0	$ 0	0	$ 1,100,000
Principal amount of debt component					$ 400,000,000.0												$ 400,000,000.0												$ 400,000,000.0	$ 250,000,000.0
Proceeds from borrowings				$ 275,000,000
Repayment of outstanding borrowings			$ 275,000,000.0
BGC Partners 8.000% Senior Notes due May 25, 2028
Debt Instrument [Line Items]
Stated interest rate																8.00%					8.00%
Long-term debt										$ 2,260,000		$ 2,260,000		2,257,000		$ 500,000
Debt issuance costs																					$ 3,400,000
Carrying amount of debt component																					346,600,000
Debt instrument, repurchased face amount																$ 500,000
BGC Partners 8.000% Senior Notes due May 25, 2028 | Senior Notes
Debt Instrument [Line Items]
Long-term debt																				$ 2,800,000
BGC Group 3.750% Senior Notes due October 1, 2024
Debt Instrument [Line Items]
Stated interest rate						3.75%				3.75%		3.75%
Interest expense recorded											2,600,000		5,300,000
BGC Group 3.750% Senior Notes due October 1, 2024 | Senior Notes
Debt Instrument [Line Items]
Long-term debt						$ 255,500,000
BGC Partners 3.750% Senior Notes due October 1, 2024
Debt Instrument [Line Items]
Stated interest rate								3.75%		3.75%		3.75%
Debt issuance costs								$ 3,900,000
Interest expense recorded											400,000		900,000
Principal amount of debt component								300,000,000.0
Carrying amount of debt component								$ 296,100,000
BGC Partners 3.750% Senior Notes due October 1, 2024 | Parent Company
Debt Instrument [Line Items]
Long-term debt																				44,500,000
BGC Partners 3.750% Senior Notes due October 1, 2024 | Senior Notes
Debt Instrument [Line Items]
Long-term debt						$ 255,500,000
BGC Group 4.375% Senior Notes due December 15, 2025
Debt Instrument [Line Items]
Stated interest rate						4.375%				4.375%		4.375%							4.375%
Long-term debt										$ 287,829,000		$ 287,829,000		287,462,000
Interest expense recorded										3,300,000	3,300,000	6,700,000	6,700,000
Redemption price as percentage of principal amount (as a percent)						101.00%
BGC Group 4.375% Senior Notes due December 15, 2025 | Senior Notes
Debt Instrument [Line Items]
Long-term debt						$ 288,200,000				$ 14,500,000		$ 14,500,000
BGC Partners 4.375% Senior Notes due December 15, 2025
Debt Instrument [Line Items]
Stated interest rate								4.375%		4.375%		4.375%
Long-term debt										$ 11,836,000		$ 11,836,000		11,824,000
Interest expense recorded										$ 100,000	100,000	$ 300,000	300,000
BGC Partners 4.375% Senior Notes due December 15, 2025 | Senior Notes
Debt Instrument [Line Items]
Long-term debt																				$ 11,800,000
BGC Group 8.000% Senior Notes due May 25, 2028
Debt Instrument [Line Items]
Stated interest rate						8.00%				8.00%		8.00%							8.00%
Long-term debt										$ 345,003,000		$ 345,003,000		344,620,000
Interest expense recorded										7,100,000	$ 7,100,000	14,300,000	$ 14,300,000
Redemption price as percentage of principal amount (as a percent)						101.00%
BGC Group 8.000% Senior Notes due May 25, 2028 | Senior Notes
Debt Instrument [Line Items]
Long-term debt						$ 347,200,000
BGC Group Notes Exchange Offer
Debt Instrument [Line Items]
Debt issuance costs						$ 900,000
Unsecured Credit Agreement | Senior revolving credit agreement
Debt Instrument [Line Items]
Maximum revolving credit															$ 700,000,000.0			$ 475,000,000.0					$ 375,000,000.0					$ 350,000,000.0
Line of credit facility, outstanding amount										81,700,000		81,700,000
Deferred financing cost										$ 3,300,000		$ 3,300,000
Average interest rate (as a percent)										6.17%	7.17%	6.17%	7.18%
Interest expense recorded										$ 2,300,000	$ 4,200,000	$ 6,300,000	$ 7,900,000
Repayment of outstanding borrowings				$ 240,000,000
Unsecured Credit Agreement | New Senior Revolving Credit Agreement
Debt Instrument [Line Items]
Line of credit facility, outstanding amount														195,800,000
Deferred financing cost														4,200,000
BGC Group 6.600% Senior Notes due June 10, 2029
Debt Instrument [Line Items]
Stated interest rate		6.60%								6.60%		6.60%
Long-term debt										$ 496,046,000		$ 496,046,000		495,546,000
Interest expense recorded										$ 8,500,000	1,900,000	$ 17,000,000.0	1,900,000
Principal amount of debt component		$ 500,000,000
BGC Partners 4.375% Senior Notes due December 15, 2025
Debt Instrument [Line Items]
Stated interest rate																										4.375%
Debt issuance costs																										$ 3,200,000
Principal amount of debt component																										300,000,000.0
Carrying amount of debt component																										$ 296,800,000
BGC Group 8.000% Senior Notes due May 25, 2028
Debt Instrument [Line Items]
Stated interest rate										8.00%		8.00%
Interest expense recorded										$ 0	100,000	$ 100,000	100,000
Principal amount of debt component																					$ 350,000,000.0
BGC Group 6.600% Senior Notes due June 10, 2029
Debt Instrument [Line Items]
Long-term debt										496,000,000.0		496,000,000.0
Debt issuance costs		5,000,000.0
Principal amount of debt component		500,000,000.0
Carrying amount of debt component		$ 495,500,000
BGC Group 6.150% Senior Notes due April 2, 2030
Debt Instrument [Line Items]
Long-term debt										693,116,000		693,116,000		0
Debt issuance costs	$ 7,200,000
Interest expense recorded										$ 10,900,000		$ 10,900,000
Carrying amount of debt component	$ 692,800,000
Redemption price as percentage of principal amount (as a percent)	101.00%	101.00%
BGC Group 6.150% Senior Notes due April 2, 2030 | Related Party | Underwriting fees
Debt Instrument [Line Items]
Stated interest rate										6.15%		6.15%
Principal amount of debt component	$ 700,000,000.0
Unsecured credit agreement | Intra-day overdraft credit line
Debt Instrument [Line Items]
Debt instrument, renewal term							90 days
Line of credit facility, fee										$ 0	$ 0	$ 100,000	$ 100,000
Unsecured credit agreement | Intra-day overdraft credit line | Itau Unibanco S.A.
Debt Instrument [Line Items]
Maximum revolving credit							$ 12,800,000		$ 9,200,000													R$ 70.0		$ 11,000,000.0	R$ 60.0						R$ 50.0
Line of credit facility, outstanding amount										$ 0		$ 0		$ 0
Line of credit facility, fee percentage (as a percent)									1.32%